Abstract:
The World Magnetic Model is the standard model of the US Department of Defense, the UK Ministry of Defence, the North Atlantic Treaty Organization (NATO), and the World Hydrographic Office (WHO) navigation and attitude/heading referencing systems. It is also used widely in civilian navigation systems. The model, associated software, and documentation are distributed by NGDC on behalf of NGA. The ... model is produced at 5-year intervals, with the current model expiring on December 31, 2009. http://www.ngdc.noaa.gov/seg/WMM/DoDWMM.shtml

The WMM consists of a degree and order 12 spherical-harmonic main (i.e., core-generated) field model comprised of 168 spherical-harmonic Gauss coefficients and degree and order 12 spherical-harmonic Secular-Variation (SV) (core-generated, slow temporal variation) field model (determined to degree and order 8). WMM2005 supersedes WMM2000 and should replace this model in navigation systems. Also included with the model is computer software (available in FORTRAN or C) for computing the magnetic field components X, Y, Z, F, D, I, and H in geodetic coordinates. The spherical-harmonic expansions used to compute the magnetic field components are described in the NOAA Technical Report: The US/UK World Magnetic Model for 2005-2010

The World Magnetic Model is a product of the United States National Geospatial-Intelligence Agency (NGA). The U.S. National Geophysical Data Center (NGDC) and the British Geological Survey (BGS) produced the WMM with funding provided by NGA in the USA and by the Defence Geographic Imagery and Intelligence Agency (DGIA) in the UK.

Access Constraints
This site provides access to the DoD software and current WMM model. The software computes the main components of the geomagnetic field and their annual changes. The programs are designed to be used in demand mode. The software is available in both C and Fortran source code. The model file, wmm.cof, is expected to reside in the same directory as the software. Note: The altitude is referenced to the World Geodetic System 1984 (WGS 84) ellipsoid.